The 1703 Apennine earthquakes were a sequence of three earthquakes of magnitude ≥6 that occurred in the central Apennines of Italy, over a period of 19 days. The epicenters were near Norcia (14 January), Montereale (16 January) and L'Aquila (2 February), showing a southwards progression over about 36 km. These events involved all of the known active faults between Norcia and L'Aquila.[1] A total of about 10,000 people are estimated to have died as a result of these earthquakes,[2] although because of the overlap in areas affected by the three events, casualty numbers remain highly uncertain.

There was extensive damage in the area around Norcia, with Spoleto and Rieti also affected.[6] Modern estimates give a maximum Mercalli intensity of XI (Extreme).[7]Ground rupture was observed at several locations and these have been confirmed by modern investigations.[1]

The earthquake occurred at 13:30 UTC on 16 January with an estimated magnitude of 6.2.[5] It is thought to have been caused by movement on the Montereale Fault.[1] Damage was recorded in Montereale, Cittareale, Accumoli and Amatrice. Although of lower magnitude than the other two events, this earthquake was still felt in Rome.[6] The estimated intensity for this event is VIII (Severe).[7] No separate casualty figures are available for this event.

Most of the buildings in L’Aquila were badly damaged or completely destroyed. Damage was reported from as far away as Rome.[6] Modern estimates give a maximum intensity of X (Extreme).[7] The earthquake caused a huge landslide on the Mt. Marine ridge, a large slope failure near Posta and liquefaction along the Aterno River.

Some seismologists interpret these events as related. It has been suggested that the Norcia earthquake led directly to the Montereale event, which had the effect of further loading the fault at Aquila, thus triggering the final event.[1] Such sequential adjacent events are examples of Coulomb stress transfer.

1.
Italy
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Italy, officially the Italian Republic, is a unitary parliamentary republic in Europe. Located in the heart of the Mediterranean Sea, Italy shares open land borders with France, Switzerland, Austria, Slovenia, San Marino, Italy covers an area of 301,338 km2 and has a largely temperate seasonal climate and Mediterranean climate. Due to its shape, it is referred to in Italy as lo Stivale. With 61 million inhabitants, it is the fourth most populous EU member state, the Italic tribe known as the Latins formed the Roman Kingdom, which eventually became a republic that conquered and assimilated other nearby civilisations. The legacy of the Roman Empire is widespread and can be observed in the distribution of civilian law, republican governments, Christianity. The Renaissance began in Italy and spread to the rest of Europe, bringing a renewed interest in humanism, science, exploration, Italian culture flourished at this time, producing famous scholars, artists and polymaths such as Leonardo da Vinci, Galileo, Michelangelo and Machiavelli. The weakened sovereigns soon fell victim to conquest by European powers such as France, Spain and Austria. Despite being one of the victors in World War I, Italy entered a period of economic crisis and social turmoil. The subsequent participation in World War II on the Axis side ended in defeat, economic destruction. Today, Italy has the third largest economy in the Eurozone and it has a very high level of human development and is ranked sixth in the world for life expectancy. The country plays a prominent role in regional and global economic, military, cultural and diplomatic affairs, as a reflection of its cultural wealth, Italy is home to 51 World Heritage Sites, the most in the world, and is the fifth most visited country. The assumptions on the etymology of the name Italia are very numerous, according to one of the more common explanations, the term Italia, from Latin, Italia, was borrowed through Greek from the Oscan Víteliú, meaning land of young cattle. The bull was a symbol of the southern Italic tribes and was often depicted goring the Roman wolf as a defiant symbol of free Italy during the Social War. Greek historian Dionysius of Halicarnassus states this account together with the legend that Italy was named after Italus, mentioned also by Aristotle and Thucydides. The name Italia originally applied only to a part of what is now Southern Italy – according to Antiochus of Syracuse, but by his time Oenotria and Italy had become synonymous, and the name also applied to most of Lucania as well. The Greeks gradually came to apply the name Italia to a larger region, excavations throughout Italy revealed a Neanderthal presence dating back to the Palaeolithic period, some 200,000 years ago, modern Humans arrived about 40,000 years ago. Other ancient Italian peoples of undetermined language families but of possible origins include the Rhaetian people and Cammuni. Also the Phoenicians established colonies on the coasts of Sardinia and Sicily, the Roman legacy has deeply influenced the Western civilisation, shaping most of the modern world

2.
Apennine Mountains
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The Apennines or Apennine Mountains are a mountain range consisting of parallel smaller chains extending c. 1,200 km along the length of peninsular Italy. In the northwest they join with the Ligurian Alps at Altare, in the southwest they end at Reggio di Calabria, the coastal city at the tip of the peninsula. The system forms an arc enclosing the east side of the Ligurian and Tyrrhenian Seas, the name originally applied to the north Apennines. However, historical linguists have never found a derivation with which they are universally comfortable, wilhelm Deecke said. its etymology is doubtful but some derive it from the Ligurian-Celtish Pen or Ben, which means mountain peak. The mountains lend their name to the Apennine peninsula, which forms the part of Italy. They are mostly verdant, although one side of the highest peak, Corno Grande is partially covered by Calderone glacier and it has been receding since 1794. The eastern slopes down to the Adriatic Sea are steep, while the western slopes form foothills on which most of peninsular Italys cities are located. The mountains tend to be named from the province or provinces in which they are located, for example, as the provincial borders have not always been stable, this practice has resulted in some confusion about exactly where the montane borders are. Often but not always a feature can be found that lends itself to being a border. The Apennines are divided into three sectors, northern, central, and southern, a number of long hiking trails wind through the Apennines. Of note is European walking route E1 coming from northern Europe and traversing the lengths of the northern, the Grand Italian Trail begins in Trieste and after winding through the Alpine arc traverses the entire Apennine system, Sicily and Sardinia. The northern Apennines consist of three sub-chains, the Ligurian, Tuscan-Emilian, and Umbrian Apennines, the Ligurian Apennines border the Ligurian Sea in the Gulf of Genoa, from about Savona below the upper Bormida River valley to about La Spezia below the upper Magra River valley. The range follows the Gulf of Genoa separating it from the upper Po Valley, the northwestern border follows the line of the Bormida River to Acqui Terme. There the river continues northeast to Alessandria in the Po Valley, the upper Bormida can be reached by a number of roads proceeding inland at a right angle to the coast southwest of Savona, the chief one being the Autostrada Torino-Savona. They ascend to the Bocchetta di Altare, sometimes called Colle di Cadibona,436 m, a bronze plaque fixed to a stone marks the top of the pass. In the vicinity are fragments of the old road and three ruins of former fortifications, at Carcare, the main roads connect with the upper Bormida valley before turning west. The Scrivia, the Trebbia and the Taro, tributaries of the Po River, the range contains dozens of peaks. Toward the southern end the Aveto Natural Regional Park includes Monte Penna, nearby is the highest point of Ligurian Apennines, Monte Maggiorasca at 1,780 m

3.
L'Aquila
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LAquila is a city and comune in Southern Italy, both the capital city of the Abruzzo region and of the Province of LAquila. As of 2013, it has a population of 70,967 inhabitants, laid out within medieval walls on a hill in the wide valley of the Aterno river, it is surrounded by the Apennine Mountains, with the Gran Sasso dItalia to the north-east. LAquila sits upon a hillside in the middle of a narrow valley, a maze of narrow streets, lined with Baroque and Renaissance buildings and churches, open onto elegant piazzas. There are several ski resorts in the surrounding province, close to the highest of the Apennine summits, LAquila is positioned at an elevation of 721 metres in the Valley of the Aterno-Pescara, situated between four mountain peaks above 2,000 metres. The mountains block the city off from warm air currents from the Mediterranean, and give rise to a climate that is cool in comparison to most of central Italy. It has been said that the city each year 11 cold months. LAquila is approximately 100 kilometres east-northeast of Rome, with which it is connected by an autostrada through the mountains. The citys construction was begun by Frederick II, Holy Roman Emperor and King of Sicily, out of already existing villages. The name of Aquila means Eagle in Italian, construction was completed in 1254 under Fredericks son, Conrad IV of Germany. The name was switched to Aquila degli Abruzzi in 1861, after the death of Conrad, the city was destroyed by his brother Manfred in 1259, but soon rebuilt by Charles I of Anjou, its successor as king of Sicily. The walls were completed in 1316 and it quickly became the second city of the Kingdom of Naples. It was a city, ruled by a diarchy composed of the City Council. It fell initially under the lordship of Niccolò dellIsola, appointed by the people as the Peoples Knight, later, it fell under Pietro Lalle Camponeschi, Count of Montorio, who became the third side of a new triarchy, with the Council and the Kings Captain. Camponeschi, who was also Great Chancellor of the kingdom of Naples, became too powerful and his descendants fought with the Pretatti family for power for several generations, but never again attained the power of their ancestor. In the end, however, the Aquilans had him deposed and imprisoned by the king of Naples, the Fountain of the 99 Spouts, was given its name to celebrate the ancient origin of the town. The City Council was originally composed of the Mayors of the villages, later, the Camerlengo also took political power, as President of the City Council. Negotiations for the succession of Edmund, son of Henry III of England, the pontificate of Celestine V gave a new impulse to building development, as can be seen from the city statutes. In 1311, moreover, King Robert of Anjou granted privileges which had a influence on the development of trade

4.
Fault (geology)
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In geology, a fault is a planar fracture or discontinuity in a volume of rock, across which there has been significant displacement as a result of rock-mass movement. Large faults within the Earths crust result from the action of tectonic forces. Energy release associated with movement on active faults is the cause of most earthquakes. A fault plane is the plane that represents the surface of a fault. A fault trace or fault line is the intersection of a plane with the ground surface. A fault trace is also the line commonly plotted on maps to represent a fault. Since faults do not usually consist of a single, clean fracture, the two sides of a non-vertical fault are known as the hanging wall and footwall. By definition, the wall occurs above the fault plane. This terminology comes from mining, when working a tabular ore body, because of friction and the rigidity of rocks, they cannot glide or flow past each other easily, and occasionally all movement stops. A fault in ductile rocks can also release instantaneously when the rate is too great. The energy released by instantaneous strain-release causes earthquakes, a common phenomenon along transform boundaries, slip is defined as the relative movement of geological features present on either side of a fault plane, and is a displacement vector. A faults sense of slip is defined as the motion of the rock on each side of the fault with respect to the other side. In practice, it is only possible to find the slip direction of faults. Based on direction of slip, faults can be categorized as, strike-slip. Dip-slip, offset is predominantly vertical and/or perpendicular to the fault trace, oblique-slip, combining significant strike and dip slip. The fault surface is usually vertical and the footwall moves either left or right or laterally with very little vertical motion. Strike-slip faults with left-lateral motion are known as sinistral faults. Those with right-lateral motion are known as dextral faults

5.
Spoleto
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Spoleto is an ancient city in the Italian province of Perugia in east central Umbria on a foothill of the Apennines. It is 20 km S. of Trevi,29 km N. of Terni,63 km SE of Perugia,212 km SE of Florence, and 126 km N of Rome. Spoleto was situated on the branch of the Via Flaminia. An ancient road also ran hence to Nursia, the Ponte Sanguinario of the 1st century BC still exists. The Forum lies under todays marketplace, located at the head of a large, broad valley, surrounded by mountains, Spoleto has long occupied a strategic geographical position. It appears to have been an important town to the original Umbri tribes, after the Battle of Lake Trasimene Spoletium was attacked by Hannibal, who was repulsed by the inhabitants During the Second Punic War the city was a useful ally to Rome. It suffered greatly during the wars of Gaius Marius and Sulla. The latter, after his victory over Marius, confiscated the territory of Spoletium, from this time forth it was a municipium. Under the empire it seems to have flourished once again, but is not often mentioned in history, aemilianus, who had been proclaimed emperor by his soldiers in Moesia, was slain by them here on his way from Rome, after a reign of three or four months. Rescripts of Constantine and Julian are dated from Spoleto, owing to its elevated position Spoleto was an important stronghold during the Vandal and Gothic wars, its walls were dismantled by Totila. Under the Lombards, Spoleto became the capital of an independent duchy, the Duchy of Spoleto, in 774 it became part of Holy Roman Empire. Together with other fiefs, it was bequeathed to Pope Gregory VII by the powerful countess Matilda of Tuscany, in 1155 it was destroyed by Frederick Barbarossa. In 1213 it was occupied by Pope Gregory IX. After Napoleons conquest of Italy, in 1809 Spoleto became capital of the short-lived French department of Trasimène, returning to the Papal States after Napoleons defeat, in 1860, after a gallant defence, Spoleto was taken by the troops fighting for the unification of Italy. Giovanni Pontano, founder of the Accademia Pontaniana of Naples, was born here, the stage is occupied by the former church of St. Agatha, currently housing the National Archaeological Museum. Ponte Sanguinario, a Roman bridge 1st century BCE, the name is traditionally attributed to the persecutions of Christians in the nearby amphiteatre. A restored Roman house with floors, indicating it was built in the 1st century. An inscription by Polla to Emperor Caligula suggests the house was that of Vespasia Polla and it was turned into a fortress by Totila in 545 and in Middle Ages times was used for stores and shops, while in the cavea the church of San Gregorio Minore was built

6.
Rieti
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Rieti is a city and comune in Lazio, central Italy, with a population of 47,700. It is the capital of province of Rieti and see of the diocese of Rieti, the town centre rests on a small hilltop, commanding from the southern edge the wide Rieti valley, at the bottom of Sabine mountains and of monti Reatini, among which mount Terminillo. The plain was once a lake, drained by ancient Romans. Only the small Ripasottile and Lungo lakes remain of the large one. According to the legend, Reate was founded by Rea, a divinity and it was founded at the beginning of the Iron Age. Probably in earlier times the lands around Rieti were inhabited by Umbri, then by Aborigines and later on by Sabines, Reate was originally a major site of the Sabine nation well before the foundation of Rome. According to the legend, when Romulus founded Rome, Romans kidnapped Sabine women in order to populate the town, so there was a war between Romans and Sabines. The battle of the Lacus Curtius came to an end only when the women threw themselves among the armies, Romulus and Titus Tatius reprieved and a collaboration between the two people started. According to a version based on history, Sabines settled on the Quirinale because of their continuous need. Many lands of Reate and Amiternum were confiscated and allocated to Romans, at the very beginning, Sabines were offered Roman citizenship but with no right of voting, but yet in 268 BC they gained the full citizenship, being included in two new tribes. Curius Dentatus drained a large portion of the lake by making the Velino a distributary of the Nera river, the wide area once occupied by the lake turned into a fertile plain. Following Roman customs, the land was split into characteristic square allotments, the town itself underwent significant development, being re-organised according to typical Roman urbanistic standards, and was fortified with strong walls. A stone bridge was laid across the Velino river, and a viaduct was built to bring goods from the Salaria road directly to Rietis southern door. Roman Reate receives a number of mentions in Latin literature, thanks to its soil, its valued assets. Cicero, for instance, describes the tensions between Reate and Interamna following the drainage, and refers to the country houses that his friend Q. One of the most important Sabine families that gained success in Rome was the Gens Flavia, the Reatin poet and writer Marcus Terentius Varro was born in 116 BC and he is usually referred to as the father of Roman erudition. After the fall of the Western Roman Empire Rieti suffered destruction by Barbarians, under the Franks, it was county capital. It was sacked by the Saracens in the 9th and 10th century, the city was rebuilt with the help of the Roman comune, and from 1198 was also a free commune, of Guelph orientation, with a podestà of its own

7.
Soil liquefaction
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In soil mechanics the term liquefied was first used by Allen Hazen in reference to the 1918 failure of the Calaveras Dam in California. The phenomenon is most often observed in saturated, loose, sandy soils and this is because a loose sand has a tendency to compress when a load is applied, dense sands by contrast tend to expand in volume or dilate. If the soil is saturated by water, a condition that exists when the soil is below the ground water table or sea level. In response to the soil compressing, this increases in pressure. These contacts between grains are the means by which the weight from buildings and overlying soil layers are transferred from the surface to layers of soil or rock at greater depths. This loss of soil structure causes it to all of its strength. Although the effects of liquefaction have been understood, it was more thoroughly brought to the attention of engineers after the 1964 Niigata earthquake and 1964 Alaska earthquake. It was also a factor in the destruction in San Franciscos Marina District during the 1989 Loma Prieta earthquake. A state of soil liquefaction occurs when the stress of soil is reduced to essentially zero. This may be initiated by either monotonic loading or cyclic loading, in both cases a soil in a saturated loose state, and one which may generate significant pore water pressure on a change in load are the most likely to liquefy. As pore water pressure rises a progressive loss of strength of the soil occurs as effective stress is reduced and it is more likely to occur in sandy or non-plastic silty soils, but may in rare cases occur in gravels and clays. A flow failure may initiate if the strength of the soil is reduced below the required to maintain equilibrium of a slope or footing of a building for instance. This can occur due to loading or cyclic loading, and can be sudden. A historical example is the Aberfan disaster, casagrande referred to this type of phenomena as flow liquefaction although a state of zero effective stress is not required for this to occur. The term cyclic refers to the occurrence of a state of soil when large shear strains have accumulated in response to cyclic loading. A typical reference strain for the occurrence of zero effective stress is 5% double amplitude shear strain. This is a soil test based definition, usually performed via cyclic triaxial, cyclic direct simple shear and these tests are performed to determine a soils resistance to liquefaction by observing the number of cycles of loading at a particular shear stress amplitude before it fails. Failure here is defined by the shear strain criteria

8.
United States Geological Survey
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The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its resources. The organization has four science disciplines, concerning biology, geography, geology. The USGS is a research organization with no regulatory responsibility. The USGS is a bureau of the United States Department of the Interior, the USGS employs approximately 8,670 people and is headquartered in Reston, Virginia. The USGS also has major offices near Lakewood, Colorado, at the Denver Federal Center, the current motto of the USGS, in use since August 1997, is science for a changing world. The agencys previous slogan, adopted on the occasion of its anniversary, was Earth Science in the Public Service. Prompted by a report from the National Academy of Sciences, the USGS was created, by a last-minute amendment and it was charged with the classification of the public lands, and examination of the geological structure, mineral resources, and products of the national domain. This task was driven by the need to inventory the vast lands added to the United States by the Louisiana Purchase in 1803, the legislation also provided that the Hayden, Powell, and Wheeler surveys be discontinued as of June 30,1879. Clarence King, the first director of USGS, assembled the new organization from disparate regional survey agencies, after a short tenure, King was succeeded in the directors chair by John Wesley Powell. Administratively, it is divided into a Headquarters unit and six Regional Units, Other specific programs include, Earthquake Hazards Program monitors earthquake activity worldwide. The National Earthquake Information Center in Golden, Colorado on the campus of the Colorado School of Mines detects the location, the USGS also runs or supports several regional monitoring networks in the United States under the umbrella of the Advanced National Seismic System. The USGS informs authorities, emergency responders, the media, and it also maintains long-term archives of earthquake data for scientific and engineering research. It also conducts and supports research on long-term seismic hazards, USGS has released the UCERF California earthquake forecast. The USGS National Geomagnetism Program monitors the magnetic field at magnetic observatories and distributes magnetometer data in real time, the USGS operates the streamgaging network for the United States, with over 7400 streamgages. Real-time streamflow data are available online, since 1962, the Astrogeology Research Program has been involved in global, lunar, and planetary exploration and mapping. USGS operates a number of related programs, notably the National Streamflow Information Program. USGS Water data is available from their National Water Information System database

9.
1693 Sicily earthquake
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The 1693 Sicily earthquake struck parts of southern Italy near Sicily, Calabria and Malta on January 11 at around 21,00 local time. This earthquake was preceded by a damaging foreshock on January 9 and it had an estimated magnitude of 7. The earthquake was followed by tsunamis that devastated the coastal villages on the Ionian Sea, almost two thirds of the entire population of Catania were killed. The epicentre of the disaster was probably close to the coast, possibly offshore, Sicily lies on part of the complex convergent boundary where the African Plate is subducting beneath the Eurasian Plate. This subduction zone is responsible for the formation of the stratovolcano Mount Etna, most damaging earthquakes however, occur on the Siculo-Calabrian rift zone. Faults in the Calabrian segment were responsible for the 1783 Calabrian earthquakes sequence, in the southern part of the eastern coast of Sicily, investigations have identified a series of active normal faults, dipping to the east. Most of these lie offshore and some control basins that contain large thicknesses of Quaternary sediments, the two largest faults, known as the western and eastern master faults, border half-grabens with fills of up to 700 metres and 800 metres respectively. A destructive earthquake occurred two days before the mainshock at 21,00 local time, centered in the Val di Noto and it had an estimated magnitude of 6.2 and a maximum perceived intensity of VIII–XI on the Mercalli intensity scale. Intensities of VIII or higher have been estimated for Augusta, Avola Vecchia, Floridia, Melilli, Noto Antica, Catania, Francofonte, Lentini, Scicli, Sortino and Vizzini. Augusta lies well outside the zone of severe shaking, its extensive damage is probably due to its construction on unconsolidated sediments. From the shape and location of the area of maximum damage, the earthquake lasted for four minutes, according to contemporary accounts. The estimated magnitude of 7.4 is taken from the extent and degree of the recorded damage, the source of the January 11 earthquake is debated. A landslide origin is supported by the observation of possible landslide bodies along the Hyblean-Malta escarpment, historic documents in the Archivo General de Simancas mention dozens of aftershocks, some as late as August 1694, and some reportedly as strong as the initial quake of January 11,1693. Aftershocks continued until at least 1696, with their effects concentrated in towns along the coast, the tsunami triggered by the earthquake affected most of the Ionian Sea coast of Sicily, about 230 kilometres in all. The first thing that was noted at all localities affected was a withdrawal of the sea, the maximum inundation of about 1.5 kilometres was recorded at Mascali. Tsunami deposits linked to the 1693 tsunami have been found both onshore and offshore, at Ognina, just south of Syracuse, at the head of a ria, a sequence containing several coarse clastic layers has been found, inconsistent with its lagoonal setting. The uppermost coarse layer, which has a strongly erosive base, the layer has been dated as 17th to 18th century based on pottery shards and one well-preserved clay pipe, consistent with the 1693 tsunami. Offshore from Augusta, a sequence identified using chirp sonar data was sampled with a 6.7 metres gravity core in 72 metres of water, the uppermost two events correlate well with the tsunamis from the 1908 Messina earthquake and the 1693 earthquake

10.
1908 Messina earthquake
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The 1908 Messina earthquake occurred on 28 December in Sicily and Calabria, southern Italy with a moment magnitude of 7.1 and a maximum Mercalli intensity of XI. The cities of Messina and Reggio Calabria were almost completely destroyed, on Monday 28 December 1908, from about 05,20 to 05,21, an earthquake of 7.1 on the moment magnitude scale occurred. Its epicentre was in the Strait of Messina which separates the port city of Messina in Sicily. Its precise epicentre has been pinpointed to the northern Ionian Sea area close to the narrowest section of the Strait and it had a depth of 5–6 miles. At least 91% of structures in Messina were destroyed or irreparably damaged and some 75,000 people were killed in the city, Reggio Calabria and other locations in Calabria also suffered heavy damage, with some 25.000 people killed. Reggios historic centre was almost completely eradicated. The number of casualties is based on the 1901 and 1911 census data and it was the most destructive earthquake to ever strike Europe. The ground shook for some 30 to 40 seconds, and the damage was widespread, in Calabria, the ground shook violently from Scilla to south of Reggio, provoking landslides inland in the Reggio area and along the sea-cliff from Scilla to Bagnara. In the Calabrian commune of Palmi on the Tyrrhenian coast, there was almost total devastation that left 600 dead, damage was also inflicted along the eastern Sicilian coast, but outside of Messina, it was not as badly hit as Calabria. The mesoseismal area was confined near the coast along a 1–4 km wide belt that shook and destroyed Messina, catania, the largest city in eastern Sicily, did not incur notable damage. a circular motion. The elevated death toll was due to the fact that most people were asleep, thousands were trapped under debris, suffering horrific injuries of which many would die. One week before the earthquake,160,000 inhabitants were counted in the entire Messina commune, about ten minutes after the earthquake, the sea on both sides of the Strait suddenly withdrew a 12-meter tsunami swept in, and three waves struck nearby coasts. It impacted hardest along the Calabrian coast and inundated Reggio Calabria after the sea had receded 70 meters from the shore, the entire Reggio seafront was destroyed and numbers of people who had gathered there perished. Nearby Villa San Giovanni was also badly hit, along the coast between Lazzaro and Pellaro, houses and a railway bridge were washed away. In Messina, the tsunami also caused more devastation and deaths, the second and third tsunami waves, coming in rapid succession and higher than the first, raced over the harbour, smashed boats docked at the pier, and broke parts of the sea wall. The ships that were attached to their moorings collided with one another. Afterwards Messina harbour was filled with floating wreckage and the corpses of drowned people, towns and villages along the eastern coast of Sicily were assaulted by high waves causing deaths and damage to boats and property. Two hours later the tsunami struck Malta, about 2000 people were killed by the tsunami in Messina, the eastern coast of Sicily, and in Reggio Calabria and its coastal environs. The Messina shoreline was irrevocably altered as large sections of the coast had sunk several feet into the sea, houses, churches, palaces and monuments, military barracks, commercial, municipal and public buildings had all collapsed entirely or were severely damaged

11.
Earthquake
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An earthquake is the shaking of the surface of the Earth, resulting from the sudden release of energy in the Earths lithosphere that creates seismic waves. Earthquakes can range in size from those that are so weak that they cannot be felt to those violent enough to people around. The seismicity or seismic activity of an area refers to the frequency, type, Earthquakes are measured using measurements from seismometers. The moment magnitude is the most common scale on which earthquakes larger than approximately 5 are reported for the entire globe and these two scales are numerically similar over their range of validity. Magnitude 3 or lower earthquakes are mostly imperceptible or weak and magnitude 7 and over potentially cause damage over larger areas. The largest earthquakes in historic times have been of magnitude slightly over 9, intensity of shaking is measured on the modified Mercalli scale. The shallower an earthquake, the damage to structures it causes. At the Earths surface, earthquakes manifest themselves by shaking and sometimes displacement of the ground, when the epicenter of a large earthquake is located offshore, the seabed may be displaced sufficiently to cause a tsunami. Earthquakes can also trigger landslides, and occasionally volcanic activity, in its most general sense, the word earthquake is used to describe any seismic event — whether natural or caused by humans — that generates seismic waves. Earthquakes are caused mostly by rupture of faults, but also by other events such as volcanic activity, landslides, mine blasts. An earthquakes point of rupture is called its focus or hypocenter. The epicenter is the point at ground level directly above the hypocenter, tectonic earthquakes occur anywhere in the earth where there is sufficient stored elastic strain energy to drive fracture propagation along a fault plane. The sides of a fault move past each other smoothly and aseismically only if there are no irregularities or asperities along the surface that increase the frictional resistance. Most fault surfaces do have such asperities and this leads to a form of stick-slip behavior, once the fault has locked, continued relative motion between the plates leads to increasing stress and therefore, stored strain energy in the volume around the fault surface. This continues until the stress has risen sufficiently to break through the asperity, suddenly allowing sliding over the portion of the fault. This energy is released as a combination of radiated elastic strain seismic waves, frictional heating of the fault surface and this process of gradual build-up of strain and stress punctuated by occasional sudden earthquake failure is referred to as the elastic-rebound theory. It is estimated that only 10 percent or less of a total energy is radiated as seismic energy. Most of the energy is used to power the earthquake fracture growth or is converted into heat generated by friction

Normal fault in the Bozeman Group near the Harrison Reservoir, Montana

A fault in Morocco.The fault plane is the steeply leftward-dipping line in the centre of the photo, which is the plane along which the rock layers to the left have slipped downwards, relative to the layers to the right of the fault.

Back-arc basins are geologic basins, submarine features associated with island arcs and subduction zones. They are …

Cross-section through the shallow part of a subduction zone showing the relative positions of an active magmatic arc and back-arc basin, such as the southern part of the Izu-Bonin-Mariana Arc.

Cross-section sketch showing the development of a back-arc basin by rifting the arc longitudinally. The rift matures to the point of seafloor spreading, allowing a new magmatic arc to form on the trenchward side of the basin (to the right in this image) and stranding a remnant arc on the far side of the basin (to the left in this image).

The active back-arc basins of the world

The islands of Japan were separated from mainland Asia by back-arc spreading